1. Technical Field
The present invention relates to an antenna apparatus, a printed wiring board, a printed circuit board, a communication adapter and portable electronic equipment, and more particularly, it relates to an antenna apparatus, a printed wiring board, a printed circuit board, a communication adapter and portable electronic equipment used for high-frequency radio equipment.
2. Related Art
Hitherto, a helical dipole antenna has been used as an antenna for portable equipment, such as a portable telephone, which is high-frequency radio equipment.
This helical dipole antenna has been constructed such that it is drawn out of the housing of portable equipment when it is used or it has been used while it is accommodated in the housing.
Japanese Unexamined Patent Application Publication No. 3-175826 discloses an antenna assembly having a second antenna in the housing of portable equipment separately from a helical dipole antenna. This construction makes it possible to create a diversity (spatial diversity or angular diversity) by the helical dipole antenna and the second antenna. As the second antenna, an inverted F antenna is generally used.
Thin portable equipment of 2.4 GHz band card type employs a chip antenna using ceramic.
To form an antenna for portable equipment on a printed wiring board, ideally, an ample space is preferably secured around an antenna element in order to secure characteristics. Generally, this has easily been implemented by forming the antenna element on a surface of the printed wiring board.
The conventional helical dipole antenna has been posing a problem in that it is large in principle, making it hardly applicable to wristwatch-size portable electronic equipment or the like required to be made smaller.
Furthermore, the inverted F antenna is constructed to implement its functions by its antenna element and ground plate (earth plate) that have a predetermined physical positional relationship, exhibiting poor freedom of layout. In addition, the characteristics of the inverted F antenna depend on the area size of the ground plate, and decreasing the area leads to deteriorated characteristics. Hence, there has been a problem in that, if the mounting density of components is required to increase so as to reduce the required area of a printed wiring board, then the mounting area of components uses up the area of the printed wiring board, and the area of the ground plate cannot be secured, making it impossible to obtain desired characteristics of the inverted F antenna.
In the case of a ceramic chip antenna, the chip antenna itself has a size that permits surface mounting. To mount the chip antenna, however, a large ground area is required to obtain desired characteristics of the antenna, leading to a problem in that the entire antenna apparatus including a peripheral circuit and the ground will be large. There is another problem of the chip antenna being expensive.
Accordingly, an object of the present invention is to provide an antenna apparatus, a printed wiring board, a printed circuit board, a communication adapter and portable electronic equipment that make it possible to improve the mounting density of an entire circuit and to achieve a smaller printed wiring board while securing the characteristics (sensitivity, in particular) of an antenna.